replace nix getgroups by rustix

[oech3]

No description provided.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/pid-pipe. tests/tail/pid-pipe is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/retry (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/rm/many-dir-entries-vs-OOM is now being skipped but was previously passing.
Skip an intermittent issue tests/pr/bounded-memory (was skipped on 'main', now failing)

[xtqqczze]

Out of interest, what is the benefit of replacing nix with rustix in tests?

[oech3]

to reduce build time in the future

[xtqqczze]

To be honest, removing nix is likely to only make a very marginal gain to build times. You can investigate using:

cargo build --timings

[sylvestre]

to me, it is to avoid having several crates doing the same things. makes the code nicer and more consistent.

[oech3]

How about removing unsafe libc (allowing nix), and removing nix later?

[xtqqczze]

How about removing unsafe libc (allowing nix), and removing nix later?

Let's move that discussion to this issue: #9549.